High-Temperature Behavior of SCC Self-Compacting/Self-Consolidating Concrete ACI Spring Convention...

High-Temperature Behavior of SCC

Self-Compacting/Self-Consolidating

Concrete

Patrick Bamonte and Pietro G. Gambarova

Dept. of Structural Engineering

Politecnico di Milano, Milan - Italy

ACI Spring Convention 2012 - Dallas

Committee 237 – Self-Consolidating Concrete

March 19, 2012

ACI Committee 237 – Dallas (TX), March 19, 2012

Introduction

1. Question : Why should SCC behave differently from ordinary

vibrated concrete – VC at high temperature and in fire ?

2. Answer : Because of the somewhat different microstructure:

►the amounts of cement, water and fine aggregates are similar to

►those in VC (70-80% by mass), but SCC typically contains:

• less medium and coarse aggregates (30% vs. 50% in VC).

• ultrafines (up to 10-15% by mass).

• relatively large amounts of chemical admixtures (superplasticizers,

viscosity agents, …).

3. Hence, the cementitious matrix is more compact, with less

interconnected pores, higher vapor-pressure build-ups in the pores at

high temperature, higher tensile stresses around the pores and more

microstructural damage

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3 VC mechanical behavior (1)

Uniaxial compression and tension

Elastic modulus

fc20 = 40 MPa (Takeuchi et al.)


4 VC mechanical behavior (2)

Hot tests on stressed/unstressed specimens

Residual tests on unstressed specimens


ACI and FIB provisions for the mechanical

decay of vibrated concrete: High temperature - Past cooling

Calcareous-siliceous aggregates

Stressed-unstressed specimens

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Different thermal ramps and specimens

geometry

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7 Test results examined in this study (1)

• 9 experimental campaigns (2004-2011); only SCC mixes; fc20 = 40-90

MPa, vf 0.2% (pp fibers); unstressed specimens

• Milan (2008-2011): , hot and residual tests, T = 20, 200, 400, 600°C; cylindrical specimens ( = 100 mm, h = 200 mm); fc = 52, 82, 90 MPa; 3 mixes; no fibers; limestone powder and mixed aggregates.

• Persson (2004): hot and residual tests; T = 20, 200, 400, 600, 800°C; cylindrical specimens ( = 100 mm, h = 200 mm); fc = 40-88 MPa; number of the mixes examined here 10 with/without pp. fibers; limestone powder and siliceous aggregates.

• Sideris (2006): residual tests; T = 20, 100, 300, 500, 700°C; cubic specimens (side = 100 mm); Rc = 42-75 MPa; number of the mixes examined here 2 (fc = 43 and 54 MPa) without fibers; siliceous aggregates.


Test results examined in this study (2)

• Noumowé, Carré, Daoud and Toutanji (2006): residual tests; T =

20, 400°C; cylindrical specimens ( = 160 mm, h = 320 mm); fc = 75-

81 MPa with/without pp fibers; one mix examined here (fc = 76 MPa, vf

= 0.2%); silica fume and calcareous aggregates.

• Reinhardt and Stegmaier (2006): residual tests T = 20-650°C;

short cylindrical cores ( = 100 mm; h = 100 mm); fc = 33-76 MPa;

number of the mixes examined here 5 (fc = 50-76 MPa); siliceous

aggregates, fly ash and calcareous powder.

• Fares, Noumowé and Remond + (2009): residual tests; T = 20,

150, 300, 450 and 600°C; cylindrical (160 320 mm) and prismatic

specimens (100 100 400 mm); number of the mixes examined

here 2 (fc = 37 and 54 MPa); limestone filler and 70-75% siliceous

aggregates.

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Test results examined in this study (3)

• Annerel and Taerwe (2010): residual tests; T = 20, 200, 300,

550°C; cylindrical specimens ( = 106 mm, h = 320 mm); fc =

63,46 MPa; one mix examined here (fc = 63 MPa); siliceous

aggregates and limestone powder; no fibers.

• Tao, Yuan and Taerwe (2010): hot tests; T = 20, 200, 400, 600,

800°C; cylindrical specimens ( = 150 mm, h = 300 mm); fc = 22-

70 MPa; number of the mixes examined here 2 (fc = 70 and 53 MPa,

the latter with fibers); calcareous aggregates and limestone powder.

• Khaliq and Kodur (2011): hot tests; T = 20-800°C with ΔT = 100

or 50°C; cylindrical specimens ( = 75 mm; h = 150 mm); fc = 70 MPa

(average value); number of the mixes examined here 2 (one with pp

fibers); calcareous aggregates, slag and fly ash.

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SCC mechanical properties (1) Compressive strength

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SCC mechanical properties (2) Elastic modulus

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12 SCC mechanical behavior (3) Compressive strength


13 SCC mechanical behavior (4) Compressive strength


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fc20 = 50, 80, 90 MPa ; D = vhd

2 / (16ΔT)

SCC vs. VC thermal behavior Thermal diffusivity


Conclusions

• No systematic differences between VC and SCC (no fibers or minimal

amounts of pp fibers), in terms of uniaxial compressive/tensile

strength, elastic modulus, fracture energy.

• Minor differences in the stress-strain curves in compression (in SCC

more linear loading branches and steeper softening branches below

400°C).

• No differences in terms of thernal diffusivity (which controls heat

transfer by conduction).

• ACI provisions for the hot/residual properties of VC (no pre-loading in

the heating phase) seem to apply also to SCC.

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Open questions

• Effect of the confinement on SCC behavior in compression: some

data are already available.

• Effect of fiber reinforcement: pp fibers against spalling

steel fibers for toughness

Some data are already available.

• Spalling sensitivity (typical of highly-unsteady thermal conditions):

some data are available, but there are no normalized methods to

assess concrete sensitivity to spalling.

High-Temperature Behavior of SCC Self-Compacting/Self-Consolidating Concrete ACI Spring Convention...

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